The invention relates to an amplifier, in particular, a wideband amplifier with a first amplifier stage and a second amplifier stage.
Such an amplifier has an output and an input and comprises a first amplification stage and a second amplification stage, wherein the first amplification stage has an active power splitter with at least one injection point, wherein this injection point corresponds to the input of the amplifier, and at least two discharge points. The active power splitter is formed according to the principle of a traveling wave amplifier. The second amplification stage has at least two injection points and at least one discharge point, wherein this discharge point corresponds to the output of the amplifier, wherein the second amplification stage is formed as a power coupler. Such an amplifier is known from U.S. Pat. No. 4,668,920.
Amplifiers are typically formed today with the use of semiconductor components, e.g., transistors. These transistors have internal parasitic capacitances and inductances. Due to these parasitic capacitances and inductances, an input impedance and an output impedance of a transistor are dependent on frequency. These effects must be compensated for in a design of amplifiers. This is typically realized by so-called matching networks. Here, a pure real input impedance, that is, an ohmic input resistance, of the environment in which the amplifier is to be used is transformed into a corresponding complex impedance on an input of the transistor. After an amplification by the transistor, typically a transformation of the complex impedance into a pure real output impedance is performed, that is, an ohmic output resistance.
It is known to use this transformation in so-called reactively matched amplifiers.
The transformation of complex impedances into real resistances and vice versa, and thus the compensation of the disruptive effects named above, however, is possible only in a certain frequency range, so that matching amplifiers have a limited bandwidth (Bode-Fano criterion and/or maximum realizable transformation ratio). In a multi-stage amplifier (e.g., a two-stage amplifier), the active components of two successive amplification stages are adapted to each other.
A disadvantage in the reactively-matched amplifiers from the prior art, as already described, is the bandwidth restriction due to the Bode-Fano criterion and/or the maximum transformation ratio that can be realized.
Alternatively, from the prior art it is known to use so-called traveling wave amplifiers. Traveling wave amplifiers are not subject to the Bode-Fano criterion.
A disadvantage in traveling wave amplifiers according to the prior art, however, is that the amplification and output power per surface area and also the maximum achievable output power are insufficient. In comparison with corresponding reactively matched amplifiers, they also have a lower power efficiency.